Hearing aid devices feature one or a number of microphones. Electret microphones are typically used in the hearing aid devices. These and/or their downstream signal processing, if applicable, nevertheless indicate problems regarding the electromagnetic compatibility (EMC). This is due, on the one hand, to the microphone conductors operating as antennae and the impedance converters in the microphone operating as demodulators. The electromagnetic waves, which are injected across the microphone conductors, can also be already demodulated in the preamplifier.